This invention relates to film registration relative to the aperture over which the film is transported in a photographic apparatus such as a camera or a film magazine, and more particularly to apparatus for repeatably registering the film perforations accurately relative to the center of the aperture through which images are exposed on the film so that each image is centered in relation to the perforations of a frame.
The perforations in continuous rolls of photographic film, whether a double row of perforations such as in 35 millimeter film or a single row as in 46 millimeter film, is for co-acting with sprockets to transport film through the camera, film magazine or other film transporting photographic apparatus. Pin or peg registration as it applies to such film, and considering 35 millimeter film as it is the most universally used film of this type, refers to the position of the image created on the film in relation to the perforations. The images have a direct relationship to the holes in the film and when the film is in exact registration the center of the image is centered in relation to the perforations. When registration is off, the image is off-center.
Although in most still photography (35 mm, 46 mm and 70 mm) the perforations are for the sole purpose of film transport so that misalignment can be tolerated, it has become common to use the perforations for locating images with respect to each other throughout the process for creating slides for an audiovisual slide show using a multiplicity of slide projectors showing multiple images simultaneously, and also for matching images for creating of animation, computer graphics and other presentations using multiple images. They are also used for locating the transparencies in slide frames during high speed film cutting and mounting threreof. In, for example, a multi-slide projector presentation, a misregistration of two thousands of an inch on 35 millimeter film will create approximately one quarter of an inch of misregistration on a ten foot high screen at a magnification of 130 times. Such misregistration is clearly noticable and affects the presentation. Accordingly, registration of the image placed on the film and of the image in the slide mounts is critical.
Film perforation which is standarized, is controlled at the time of manufacture, but not all registration systems use the same perforation to register the film during exposure as that used in a slide mount. One of the problems is that frame of 35 mm film has eight perforations so that a perforation is not located at the center of the frame. The prior art systems usually have the registrations pins outside the exposure frame area while the slide mount registration pins engage a perforation within the frame which is located one-half pitch away from the center of the image. Since film and the pitch change size due to humidity, aging and processing, certain deviations in registration may not be controlled, but this misregistration is amplified with a camera or other film transporting device having its registration pin or pins removed from the slide mount register pin by a relatively large number of perforations.
In certain prior art systems the registration pin or pins may be placed at various distances from the slide mount registration pin, e.g., four to eight in the known systems. Moreover, certain prior art cameras and other transporting devices have a long threading path between the feed sprocket and the registration pins and the operation thereof becomes very pitch sensitive. For example, at least one known prior art registration pin is displaced by 30 perforations from the feed sprocket which results in large potential errors in film location.
In the prior art, expensive precision mechanisms are utilized to advance the film one frame with sufficient accuracy such that subsequent pinning of a perforation with the registration pin will not damage the perforation. Such precision mechanism utilize Geneva drives, Scotch yoke devices or stopping motors which may be placed quite large distances from the center of the film frame and aperture. With pliant acetate-base film a certain amount of film pitch variation can be accommodated, but other film bases cannot and if the camera or other film transporting devices are not adjusted to the pitch of the film, damage to the film or the device can result.
Thus, it can be seen that pin registration is critical in certain applications and that the location of the registration pin relative to the center of the image, and the location of the feed sprocket relative to the registration pin are significant in attaining correct registration of the film for subsequent use in slide mounts.